2. ACCELERATION: C10,S2 1

3. ACCLELERATION DEFINITION the rate at which velocity changes (includes: speeding up, slowing down, or changing directions) 2

4.  Speeding up; also called accelerating POSITIVE ACCELERATION 3

5.  Slowing down; also called deccelerating NEGATIVE ACCELERATION 4

6.  Turning, which is a change of direction, is also acceleration CHANGE of DIRECTION 5

7. Acceleration is always caused by a force (a push or a pull on something). FORCE of ACCELERATION For example: A)What force causes a bicycle to stop? o Friction caused by brakes pushing on tires o Friction caused by tires pushing on road 6

8. FORCE of ACCELERATION, continued… B) What force causes a car to turn? - Friction pushing against the side of the tires. 7

9. FORCE of ACCELERATION, continued… C) What force causes a rocket to take off? - The force of the exhaust gases pushing out the bottom of the rocket. 8

10. FORMULA of ACCELERATION

11. SI Units of ACCELERATION m/s/s or m/s 2 or even… km/h/s ** This is because you are dividing speed (m/s or km/h) by time (s) 10

12. EXAMPLE - #1 SOLVE FOR ACCELERATION: 0 km/hr 5 km/hr10 km/hr 15 km/hr20 km/hr 25 km/hr 0 sec 1 sec2 sec 3 sec 4 sec 5 sec 11 The acceleration of a motorcycle is 5 km/hr/sec (every second, the motorcycle will increase its speed by 5 km/hr)

13. EXAMPLE #2 A man jumps from a plane. His beginning speed is 100 km/hr SE (southeast), and his final speed with his parachute is 10 km/hr SE (southeast). This took 3 sec. What was his acceleration? The negative sign means that he was decelerating (slowing down). 12 a = S f – S s t a = ? S f = 10 km/hr S s = 100 km/hr t = 3 s a = (10 km/hr – 100 km/hr) 3s = -90km/hr 3s = -30km/hr/s SOLVE FOR ACCELERATION:

14. ACCELERATION REVIEW #1 1) A change in velocity (or speed) divided by the time it takes for the change to occur equals the object’s _______. 13

15. ACCELERATION REVIEW #2 2) Imagine yourself driving a car down an empty stretch of road. Describe 3 ways you could you change your acceleration. 14

16. 3) Calculate the acceleration of a bus whose speed changes from 6m/s to 12m/s over a period of 3s. ACCELERATION REVIEW #3 15

17. ANSWER: 1) The answer is acceleration. Remember that, like velocity, acceleration has a direction. A car that takes a turn has changed its acceleration, even if nothing else changes. ACCELERATION REVIEW #1 16

18. ANSWER: 2) You could step on the gas; you could also step on the brake; you could turn the wheel, or do any combination of these. ACCELERATION REVIEW #2 17

19. ANSWER: Calculate the acceleration of a bus whose speed changes from 6m/s to 12m/s over a period of 3s. ACCELERATION REVIEW #3 18 a = S f – S s t a = ? S f = 12 m/s S s = 6 m/s t = 3 s a = (12 m/s – 6 m/s) 3s = 6m/s 3s = 2 m/s/s

20. PART 2 Interpreting Graphs 19

21. You can represent the acceleration of an object with a speed-time graph speed is plotted on the vertical axis (y) time is plotted on the horizontal axis (x) Reading Graphs of Acceleration

22. An object that is speeding up will have a line that slopes upward (Ex. A) Reading Graphs of Acceleration

23. An object that is slowing down will have a line that slopes downward (Ex. C) Reading Graphs of Acceleration

24. A horizontal line represents an acceleration of zero or constant speed (Ex. B) Reading Graphs of Acceleration

25. Copy Graph Below and Label

26. 25 ACCELERATION REVIEW #4 4) When reading an acceleration graph, what variable will you find on the y- axis? On the x-axis? HINT: a = S f – S s t

27. 26 ANSWER #4 SPEED (y-axis) & TIME (x-axis) a = S f – S s t

28. ACCELERATION REVIEW #5 5) What is happening at point A in this speed-time graph? A. the object is speeding up B. the object is slowing down C. the object is at rest D. the object has a constant speed 27

29. Point A = object is speeding up LABEL THIS ON YOUR GRAPH ANSWER #5 28

30. ACCELERATION REVIEW #6 29 6) What is happening at point B in this speed-time graph? A. the object is speeding up B. the object is slowing down C. the object is at rest D. the object has a constant speed

31. ANSWER #6 30 Point B = object has a constant speed LABEL THIS ON YOUR GRAPH

32. ACCELERATION REVIEW #7 31 7) What is happening at point C in this speed-time graph? A. the object is speeding up B. the object is slowing down C. the object is at rest D. the object has a constant speed

33. ANSWER #7 32 Point C = object is slowing down LABEL THIS ON YOUR GRAPH